SR 520 - I-5 to Lake Washington - Rest of the West - Past processes

How has WSDOT identified and refined designs for the Seattle portion of the SR 520 Program?
WSDOT has been working for many years with agency partners, stakeholders, and the public to develop and analyze corridor alternatives in order to select and refine a “Preferred Alternative.” Major steps in this process are described below. All documents pertaining to these steps are available in the Resource Library .

With funding now approved, WSDOT, in collaboration with the City of Seattle, will work to complete the final design of remaining project elements and begin preparation for construction.

2019 Portage Bay Project community and stakeholder outreach

The SR 520 team conducted a six-month public engagement process in 2019 to solicit community feedback on conceptual designs for the Portage Bay Bridge and Roanoke Lid Project. A 2020 published report (pdf 2 mb) summarizes the outreach activities, the public’s design ideas for key project elements, and how WSDOT incorporated those ideas into a refined design concept. In addition, the report’s appendices (pdf 3.2 mb) contain all the verbatim comments from the community.

2016 West Side Final Concept Design Report

In February 2016, WSDOT and the city of Seattle released a report containing final concept designs for the SR 520 West Side elements:

2014-2015 West Side Design Refinements

Completing the Final Concept Design in Seattle.
State lawmakers directed WSDOT (via ESSB 6001) to continue working with the city of Seattle on exploring design elements not resolved through the 2012 Seattle Community Design Process. A team of design professionals, working in collaboration with the Seattle Design Commission and supported by WSDOT and city staff, recommended design refinements for those unresolved elements.

Portage Bay Bridge, including:

  • Inclusion of a bicycle and pedestrian path
  • Recommended box girder type bridge

Montlake lid area, including:

  • Better connections
  • Quality open space
  • Sustainability

Transit and nonmotorized connections, including:

  • Bicycle and pedestrian connections to existing and planned city networks
  • Multimodal connections across the Montlake Cut
  • Implementation and next steps of connections

2011-2012 Seattle Community Design Process

Refining the Preliminary Concept Design in Seattle.
This robust and collaborative effort between WSDOT, the city of Seattle, design professionals, and the broader public resulted in a refined corridor vision and conceptual design for unfunded portions of the SR 520 corridor in Seattle.

You can read the final report online: Seattle Community Design Process final report (PDF 31 MB).

The Seattle Community Design Process (SCDP) was an iterative process that:

  • Included seven public workshops and generated thousands of public comments
  • Informed the public about the SR 520 corridor in Seattle
  • Listened to community and stakeholder feedback regarding the project design
  • Explored design refinements and collected additional public feedback
  • Integrated best practices for urban and sustainable design into the project based on feedback received
  • Continued to collect input from agency partners and community stakeholders as the process moved forward

We worked with a design advisory group, composed of members of the general public and representatives from our partner agencies. 

We also collaborated with the Arboretum and Botanical Garden Committee, Seattle Parks and Recreation and the University of Washington to implement improvements included in the 2010 Arboretum Mitigation Plan. This plan was also used to inform the Seattle Community Design Process.

Lastly, the SCDP included work that ultimately informed the design of the West Approach Bridge North. In February 2013 the Seattle City Council approved Resolution 31427 , recommending a simple, clean structural design for the West Approach Bridge North. In line with this resolution, project elements in the Montlake area would:

  • Ensure working interim connections
  • Allow for future transportation improvements and amenities, including the Montlake lid
  • Minimize and mitigate project impacts in the surrounding community.
  • Integrate with the I-5 to Medina project’s final project design, as outlined in the preferred alternative

Results of the Seattle Community Design Process

While many well-supported design refinements were endorsed and incorporated into the preliminary concept design, the city asked WSDOT to continue exploring the design of the Portage Bay Bridge, Montlake lid, and nonmotorized connectivity through Resolution 31427, which was passed in February of 2013. WSDOT incorporated endorsed design elements in the SR 520 conceptual design.

2011 Record of Decision

Identifying and approving the Preferred Alternative.
In summer 2011, the Federal Highway Administration issued a Record of Decision approving the final EIS and confirming that the preferred alternative could be considered the project’s preliminary concept design with the federal record of decision. While WSDOT had adequate budget to complete final design of the SR 520 floating bridge and begin construction in 2012, most corridor elements in Seattle did not have funding to advance design or begin construction.

2011 Final EIS Preferred Alternative

Incorporating Preferred Alternative refinements.
The June 2011 Final Environmental Impact Statement analyzed the direct, indirect, and cumulative effects of the preferred alternative compared to the no-build alternative and the three supplemental draft EIS six-lane design options. WSDOT also incorporated the design refinements made during the ESSB 6392 workgroup process.

2010 ESSB 6392 Workgroup

Refining the preferred alternative.
During the 2010 legislative session, the Washington State Legislature passed ESSB 6392, which outlined specific areas and elements of the SR 520 project preferred alternative to refine through a multiagency process. Based on legislative direction, WSDOT, the Seattle mayor, and the Seattle City Council established a workgroup that brought together King County Metro, the University of Washington, Sound Transit, and Arboretum and Botanical Garden Committee to consider design refinements and transit connections within the preferred alternative. Technical coordination also included members from the Seattle Design Commission, Seattle Pedestrian Advisory Board, and Seattle Bicycle Advisory Board.

The workgroup recommendations included the following (among others):

  • Establish a design process to expand and refine the vision, goals, and design treatments for urban design and streetscapes.
  • Enhance bicycle and pedestrian connections.
  • Establish measures to trigger construction of a second bascule bridge across the Montlake Cut.
  • Maintain the SR 520 reversible transit/HOV ramp to and from I-5.
  • Implement noise-reduction strategies throughout the corridor.

The final report included the workgroup’s recommendations on the comprehensive design refinements and transit-connection improvements to the SR 520 preferred alternative, as well as an overview of public comment. As part of this process, workgroup participants also developed a “High Capacity Transit Planning and Financing Findings and Recommendations Report” and a “Washington Park Arboretum Mitigation Plan” (December 2010). Through this process, WSDOT and the city of Seattle also agreed to continue working with key stakeholders and the public to implement the Workgroup recommendations, develop future Seattle design processes, and address other issues raised.

2010 Supplemental Draft EIS

Analyzing alternatives and selecting a Preferred Alternative.
The January 2010 supplemental draft EIS evaluated the effects of a no-build alternative and three six-lane alternative design options. The supplemental draft EIS recommended a preferred alternative similar to the final concept design configuration in terms of its geometry, although it was wider and had a taller west approach profile. The preferred alternative:

  • Maintained the existing location of the Montlake interchange.
  • Changed the westbound off-ramp to connect separately to 24th Avenue East and Montlake Boulevard East.
  • Included a new bascule bridge over the Montlake Cut, parallel to the existing Montlake Bridge.
  • Included a 1,400-foot-long lid over Montlake Boulevard East with landscaping, ramps, transit facilities, and pathways.
  • Provided near-term transit enhancements along with the ability to accommodate potential future light rail on SR 520.

2009 Legislative Workgroup

Reviewing Options A, K and L as identified from 2008 mediation.
ESHB 2211 created the SR 520 Legislative Workgroup, a group of legislators and transportation officials, to present recommendations to the governor and Legislature on a financing strategies and design options for the SR 520 corridor. ESHB 2211 also authorized tolling on SR 520.

2007-2008 Mediation and ESSB 6099

Identifying the best six-lane alternative design options.
Three six-lane design options (options A, K, and L) were developed through a stakeholder mediation process established as part of ESSB 6099, enacted during the 2007 legislative session. The mediation process included elected officials; local, federal, and state agencies; neighborhood representatives; local organizations; and WSDOT. The process concluded with a report, the 2008 Project Impact Plan (pdf 6.54 mb), that summarizes the three identified design options.

In 2008, WSDOT, King County Metro and Sound Transit released the SR 520 High-Capacity Transit Plan (pdf 2.81 mb), which defined bus rapid transit across the corridor

2006 Draft EIS

Identifying a preliminary range of alternatives.
The August 2006 Draft EIS for the SR 520 program evaluated the no-build alternative and two build alternatives: the four-lane alternative and the six-lane alternative. Based on this analysis and public feedback, WSDOT decided to continue evaluating only the no-build alternative and six-lane alternative design options.

2000-2004 Trans-Lake Washington Project

Narrowed options to cross Lake Washington:

  • Six-lane with high-capacity transit options, including light rail
  • Eight-lane with high-capacity transit options, including light rail
  • Established SR 520 as a tolled facility

1997-2000 Trans-Lake Washington Study

Evaluated multiple options to cross Lake Washington:

  • Four-lane options
  • Six-lane options
  • Eight-lane options
  • Alternative Modes